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Old 07-18-2018, 10:36 PM   #1 (permalink)
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Anti-spray wheel brush guards for truck aero?

Hi All,

I'm wondering if anyone has tried using anti-spray wheel brush guards ( tried to post a link but i have too few posts and it wouldn't let me. Google "truck wheel arch brush" to see what I mean ) as an easy way to reduce the wheel-to-well gap and perhaps improve airflow, without having to worry about manufacturing rigid custom gap closers or wheel skirts and allowing for wheel clearances in all scenarios.

It seems to me that depending on the rigidity & brush density it may reduce a lot (if not eliminate) air mixing between the wheel well and passing air and hence improve aero. This would mostly be something that makes sense on trucks (both in the American and Australian sense of the word) looks wise but as we all know some of us don't care too much about looks anyway. Another advantage is that as neither the brushes nor the tyre are likely to be harmed by contact with each other, the design could have closer clearances in the straight-running scenario, perhaps also enhancing aero. Obviously it would still be not as good as full wheel skirts for aero, but a lot easier, and especially in the front.

Has anyone tried it and found whether there is any benefit?

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Old 07-18-2018, 11:50 PM   #2 (permalink)
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I don't recall ever seeing anyone try it.
Unless it was before 2011.
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Old 07-18-2018, 11:51 PM   #3 (permalink)
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Welcome from up over.

https://www.busybee.com.au/product/w...y-suppressant/
theas
Quote:
The Spray Suppressant brush system is designed to direct water and dust back towards the road surface

My vote is for yes they "MAY" help . I havent gotten around to accumulating building, and testing yet most will say not worth the time and $ there only purpose is making water speay into larger droplets..however the AU Co I posted the link for is saying the dust is kept in the well. This means that there is separation of the turbulent air in the well from the turbulent boundary lair flowing down the boddy.

What size wiskers are you thinking.
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Old 07-19-2018, 01:05 AM   #4 (permalink)
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Aeromodding thread, finding idea's for an SUV!:Permalink #4

Compare with hangar door seal sold in 6 ft lengths.

http://precisionbrush.com/aircraft-h...or-brush-seals
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Old 07-21-2018, 12:35 PM   #5 (permalink)
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tried it and found

Hucho says that a porous surface cannot support airflow.If there's any difference in pressure across the structure,the air will just pass though it.
The little voice in my head suggests that the brushes would frustrate mixing,and 'could' provide some benefit,but science would ask us to test it,and go with the 'evidence.'
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Old 07-21-2018, 04:49 PM   #6 (permalink)
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Those 4-6" long spray-guards are limber enough to move at their ends. 2-3" bristles might be more rigid and act as a baffle, maintaining a pressure gradient.

But still accommodating ground strikes.

Does a perforated plate pass more air when it is perpendicular or parallel to the direction of air flow?
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Old 07-21-2018, 09:40 PM   #7 (permalink)
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Quote:
Does a perforated plate pass more air when it is perpendicular or parallel to the direction of air flow?
.
Depends on hole dencity and thickness..
Airbrakes are perf plate on some jets.
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Old 07-22-2018, 12:52 AM   #8 (permalink)
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Air brakes are perpendicular [in use]. The perforations increase turbulence over a solid plate, thus increasing drag.

For the parallel case, I saw a PDF (that DDG can't find today) on using round holes on the front of the sides of cattle trucks, over horizontal rectangular slot the length of the sides (as is the fashion) to prevent animals suffocating. So location and shape/size matter.
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Old 07-22-2018, 11:14 PM   #9 (permalink)
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For rigidity a person can zip tie the bristles like a straw broom then leave the last 2" for impact forgiveness. Or even plastidip the upper into a solid surface.
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Old 07-25-2018, 10:44 AM   #10 (permalink)
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perforated

Quote:
Originally Posted by freebeard View Post
Those 4-6" long spray-guards are limber enough to move at their ends. 2-3" bristles might be more rigid and act as a baffle, maintaining a pressure gradient.

But still accommodating ground strikes.

Does a perforated plate pass more air when it is perpendicular or parallel to the direction of air flow?
I agree with gumby79,that hole density and plate thickness would matter.
The edges of the holes would make a difference too.
A sharp-edged hole would always have a severe vena contracta flow constriction.
At some degree of 'entry' rounding the vena contracta would be eliminated altogether,with the highest possible flow rate.
At perpendicular flow,the plate itself would have full separation all around it,except at its attachment point.
The holes would flow the most,as the static pressure across the membrane would be greatest.
Parallel with the flow,in free flow,there'd be no flow through the holes,as pressure alongside the plate would be identical.
In asymmetrical,parallel flow,as long as any transverse pressure gradient was present,there would be flow 'though' the plate.

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